Usually such behavior appears in page view, when there is no barline „stopping“ the hairpin. I think you need to attach a minimal project here for us to be able to help you.
The difference is the sharp on beat one. With your settings there is enough space for Dorico to draw the haipin after the barline. You can control this behaviour in the engraving options.
Yes, it’s the sharp symbol, but not just on that note. Apparently if any quarter note in that “column” of the score has an accidental, it causes all the hairpins to extend out.
So I found that setting and raised it to 3 spaces. It’s still not consistent as the attached picture shows. Part of the problem is that even though I specified the dynamic be attached to the triplet, Dorico extended the end attachment point of the hairpin to the quarter note following the triplet. Why would it do this?
Dorico is not putting hairpins from - to your selection, but covering the whole duration of the selection. If you want the Crescendo only for the triplets, select the first two triplets and create a hairpin.
Also, if you prefer, you can go to Gradual Dynamics → Advanced Options in Engraving Options, and select “Do Not Cross Barline” for your gradual dynamics.
@nradisch probably checked that, Stephen, in his most recent example, but the Tbn. part, having no barline, does not stop with the others, which looks awkward to me.
The situation where there’s a gradual dynamic ending at the start of a new bar, and the bottom staff in the system or a set of staves with barline joins, is the primary reason for the allowing/disallowing dynamics to cross barlines option.
That setting definitely fixed things for me. I guess my only quibble would be that this is buried inside an “advanced” subsection. Most settings that are in the advanced categories tend to be measurement attributes that only the most particular engraver would care about. But this setting is needed to correct a default behavior that can create a layout that is very obviously bad.